The invention relates to a small-sized contact pin package for engagement with a plug socket of approximately circular cross-section.
The small-sized contact pin package discussed herein concerns, in particular, sizes corresponding to an inside diameter of the plug socket of up to 2.5 mm, more especially approximately 1 mm. The contact pin package is intended, in particular, for connecting chips or IC modules electrically and, if necessary, also mechanically on printed-circuit boards. In this case, the plug sockets are formed by metallised, more especially tin-coated, holes in the printed-circuit boards. It is usual to insert the contact pins into such tin-coated holes and then to solder them to the rear, i.e. the side of the printed-circuit board that is remote from the chip. In addition thereto, it has also been attempted simply to insert the contact pins into the metallised holes and to establish the electrically conductive connection without any subsequent soldering. However, this entails the difficulty that the diameters of these metallised holes vary, particularly because of the production methods used for metallisation, so that reliable contact making, for example in the case of over-sized holes, is uncertain. However, since minute voltages may have to be transmitted, it is important that the contacts should be produced with a low voltage drop. In order nevertheless to do without the subsequent soldering of the contact pins, it has been attempted to work the plug pins in such a way that they are elastically deformable and elastically abut the metallisation of the internal circumference of the hole. For example, the attempt has been made to split the contact pins over a portion of their length and to joggle the branches formed by the splitting. However, it has turned out that the elasticity coming about in this connection is not sufficient in order to provide reliable contact making. It turned out, in particular, that the friction between the branches, which were still abutting each other after the splitting, impaired the elastic resilience of these branches relative to each other. It was therefore possible, for example in connection with a hole which was undersized due to a deviation from tolerance, that, because of the insufficient elastic resilience, the contact pin worked itself into the metallisation to such an extent that the metallisation was pushed aside and the contact pin abutted the non-metallised internal circumference of the hole, so that the contact-making quality was again jeopardised.